Increased assimilation efficiency and mortality rate in <i>Gammarus fossarum</i> exposed to PVC microplastics

Shredder organisms play a key role in rivers by feeding and fragmenting coarse organic matter that will then be exploited by other consumers. The effects of microplastics (MPs) on Gammarus sp., an ubiquitous genus of freshwater amphipods, and its shredding activity have been broadly investigated. However, the potential behavioral and physiological effects of different sizes of MPs on Gammarus sp. remain overlooked despite the recognized influence of MP size on MP toxicity. This study investigated the effects of a 28-day exposure to four different concentrations of two size fractions of PVC-microplastics (PVC-MPs), on Gammarus fossarum mortality rate, feeding rate, assimilation efficiency, and expression of proteins involved in key processes. Increased mortality was observed for all treatments exposed to PVC-MPs, with higher mortality in the presence of smaller PVC-MPs at the highest concentration. No protein biomarker modulation was observed in presence of PVC-MPs, suggesting that no metabolic stress but direct physical damages of PVC-MPs might have led to the observed mortalities. No difference was observed for feeding rates, but a higher assimilation efficiency was measured for individuals exposed to PVC-MPs, regardless of the concentration. This could be due to energy reallocation towards defense mechanisms or indicate a potential shift in digestive microbiota. This study highlighted the toxicity of PVC-MPs, particularly of smaller sizes and even at relatively low concentration, for Gammarus fossarum. PVC-MP pollution may therefore alter the functional integrity of river ecosystems by reducing the abundance of shredder organisms and, subsequently, the process of leaf litter decomposition.</p

Challenges and perspectives in MS-based omics approaches for ecotoxicology studies: An insight on Gammarids sentinel amphipods

The aquatic environment is one of the most complex biosystems, as organism at all trophic levels may be exposed to a multitude of pollutants. As major goals, ecotoxicology typically investigates the impact of toxic pollutants on the ecosystems through the study of sentinel organisms. Over the past decades, Mass Spectrometry (MS)-based omics approaches have been extended to sentinel species both in laboratory and field exposure conditions. Single-omics approaches enable the discovery of biomarkers mirroring the health status of an organism. By covering a restricted set of the molecular cascade, they turn out to only partially satisfy the understanding of complex ecotoxicological effects. In contrast, a more complete understanding of the ecotoxicity pathways can be accessed through multi-omics approaches. In this perspective, we provide a state-of-the-art and a critical evaluation on further developments in MS-based single and multi-omics studies in aquatic ecotoxicology. As case example, literature regarding Gammarids freshwater amphipods, non-model sentinel organisms sensitive to pollutants and environmental changes and crucial species for downstream ecosystems, will be reviewed.</jats:p

Development of a multi-omics extraction method for ecotoxicology: investigation of the reproductive cycle of Gammarus fossarum

International audienceOmics study exemplified by proteomics, lipidomics or metabolomics, provides the opportunity to get insight of the molecular modifications occurring in living organisms in response to contaminants or in different physiological conditions. However, individual omics discloses only a single layer of information leading to a partial image of the biological complexity. Multiplication of samples preparation and processing can generate analytical variations resulting from several extractions and instrumental runs. To get all the -omics information at the proteins, metabolites and lipids level coming from a unique sample, a specific sample preparation must be optimized. In this study, we streamlined a biphasic extraction procedure based on a MTBE/Methanol mixture to provide the simultaneous extraction of polar (proteins, metabolites) and apolar compounds (lipids) for multi-omics analyses from a unique biological sample by a liquid chromatography (LC)/mass spectrometry (MS)/MS-based targeted approach. We applied the methodology for the study of female amphipod Gammarus fossarum during the reproductive cycle. Multivariate data analyses including Partial Least Squares Discriminant Analysis and multiple factor analysis were applied for the integration of the multi-omics data sets and highlighted molecular signatures, specific to the different stages

Dynamic Multiple Reaction Monitoring of amphipod Gammarus fossarum caeca expands molecular information for understanding the impact of contaminants

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Determination of biomarkers threshold values and illustration of their use for the diagnostic in large-scale freshwater biomonitoring surveys

Abstract Background Several biomarkers developed from freshwater sentinel species are used to complement chemical assessment of freshwater ecosystems and improve the evaluation of their contamination levels. While active biomonitoring strategies allow to compare biological data in the field, the lack of assessment criteria to interpret biomarkers modulations restricts their application in freshwater biomonitoring surveys. For this purpose, the determination of threshold values emerges as a relevant approach to support the biomarker-based diagnosis within biomonitoring surveys. Based on the distribution of contamination baselines, a statistical approach was proposed to define threshold values of bioaccumulated concentrations in the sentinel species Gammarus fossarum . Although this methodology is limited to chemical databases, this approach could be adapted for defining threshold values at the biological level. This study aims to demonstrate the possibility of defining threshold values for different classes of biomarkers monitored in two freshwater sentinel species ( Dreissena polymorpha , G. fossarum ) and evidence the added value of such an approach in biomarker-based diagnosis. Results For this purpose, the study benefited from exceptional environmental biomarker datasets acquired from mussels and gammarids caged in hundred environmental sites, representative of the diversity of French water bodies. Thanks to these environmental datasets, inhibition and/or induction thresholds could be defined for 8 biochemical, cellular, and molecular biomarkers of D. polymorpha and 25 peptide biomarkers of G. fossarum, not influenced by confounding factors. Threshold values were then applied to another biomarker dataset acquired from mussels and gammarids caged upstream and downstream four wastewater treatment plants (WWTPs). Several biomarkers were modulated both downstream and upstream of WWTPs, indicating a potential contamination not related to WWTPs. In contrast, some biomarkers were impacted exclusively downstream of the WWTPs, highlighting an impact of WWTP discharges on the aquatic fauna. Conclusions This study demonstrates the possibility to define threshold values for a wide range of biomarkers (cellular, biochemical and molecular) monitored on different sentinel species. The definition of threshold values constitutes an attractive solution to support the application of biomarkers in active biomonitoring surveys and improve the biomarker-based diagnosis without the need of “reference sites”

Organ-oriented proteogenomics functional atlas of three aquatic invertebrate sentinel species

Abstract Proteogenomic methodologies have enabled the identification of protein sequences in wild species without annotated genomes, shedding light on molecular mechanisms affected by pollution. However, proteomic resources for sentinel species are limited, and organ-level investigations are necessary to expand our understanding of their molecular biology. This study presents proteomic resources obtained from proteogenomic analyses of key organs (hepatopancreas, gills, hemolymph) from three established aquatic sentinel invertebrate species of interest in ecotoxicological/ecological research and environmental monitoring: Gammarus fossarum, Dreissena polymorpha, and Palaemon serratus. Proteogenomic analyses identified thousands of proteins for each species, with over 90% of them being annotated to putative function. Functional analysis validated the relevance of the proteomic atlases by revealing similarities in functional annotation of catalogues of proteins across analogous organs in the three species, while deep contrasts between functional profiles are delimited across different organs in the same organism. These organ-level proteomic atlases are crucial for future research on these sentinel animals, aiding in the evaluation of aquatic environmental risks and providing a valuable resource for ecotoxicological studies